This invention relates generally to movable towers for facilitating construction and maintenance work at elevated heights and more particularly to collapsible, nestable towers.
Extendable towers are well known in the construction, servicing, maintenance, and lighting tower industry. Collapsibility has facilitated portability and versatility in the range of useful heights of these towers. Heretofore, various pressurized cylinder means have been employed as the moving force for extending and collapsing or compressing the individual telescoping frame members. These pressurized extendable cylinders require either an external source of compressed fluid or a compressor or fluid pump for activation. Such towers are disclosed in U.S. Pat. Nos. 3,958,376, 3,099,332, and 3,752,261. The added expense for these cylinders represents a considerable added portion to the total price. Scissors-type linkage, as disclosed in U.S. Pat. No. 3,700,070 is an alternate mode of raising and lowering a work platform. However, this device also incorporates pressurized telescoping cylinders as the prime mover.
The present invention discloses a new and improved multi-stage telescoping tower having, as its prime moving source of power at least one helix wrapped torsion spring functionally interconnected between adjacent telescoping frame members. After a height control means is used to position the height of the upper work platform at a desired level, a locking means then positively holds that level until the user releases the locking means and repositions the work surface. This height control means may be power operation.